Revert "Don't use session to store pageLimit, breaks IR 0.7.1. Don't need it anyway."

This reverts commit c224d48ffba5e07c5811efc98fb8865f3773f5bb.
Fix 'load more' pagination (#44). Broken in c224d48.

- Works around issue with IR 0.7.1
- https://github.com/EventedMind/iron-router/issues/624